Root mealybugs and their management in horticultural crops in India

Root mealybugs feed on root, basal stem touching the soil and root hairs of plants. As many as 16 species of mealybugs are known to attack horticultural crops like banana, black pepper, betelvine, coffee, sweet potato and elephant foot yam. Infested plants are associated with ant colonies in the rhizosphere by which mealybug infestation could be easily recognised. The species belonging to genera Geococcus, Rhizoecus and Formicoccus are widely known to cause damage to pot & greenhouse plants and also field crops in India. They are colonized in junction of lateral roots with the main root, and suck the sap resulting in drying of such roots; general weakening of the plants, yellowing and narrowing of leaves and finally reduction in yield. Higher population of root mealybugs was observed in cooler months (November-January, and lowest in rainy months (June-July). Six ant species were associated with root mealybugs infestingblack pepper. Natural enemy complex is very poor on root mealybugs. However the Lycaenid Spalgis epeus Westwood and the coccinellids Scymnus sp. and Horniolus spp. were found feeding on mealybugs infesting basal stem touching the soil. Among the fungal pathogens screened, Lecanicillium lecanii Zimmerman was found better in causing mortality of root mealybug F. polysperes. Aqueous suspension of Entomopathogenic nematode Heterorhabditis was more efficient with 70% control efficiency against coffee root mealybug. There was 50% reduction in the banana root mealybug population by soil drenching with Nimbicidine (1%) and neem seed kernel extract (5%). Application of Sodium silicate and calcium oxide at the time of planting effectively reduced the mealybug Geococcus spp. in banana. Among the chemicals, soil drenching with imidacloprid 0.0125%, chlorpyriphos 0.075%, acetamiprid 0.0125% and carbosulfan 0.075% were highly effective against the root mealybugs in black pepper and banana.